Melt-flowable materials and method of sealing surfaces

ABSTRACT

The invention provides a method for imparting topographical or protective features to a substrate by contacting a sheet material comprising a thermosettable layer with a substrate and heating the sheet material to an elevated temperature.

This application is a continuation of application No. 08/421,055, filedon Apr. 12, 1995, which is a continuation-in-part of U.S. Ser. No.08/047,862, filed Apr. 15, 1993, pending and U.S. Ser. No. 08/150,692,filed Nov. 10, 1993, now abandoned, the contents of each of which arehereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method of using a melt-flowable sheetmaterial to provide protective and aesthetic features to a surface.

BACKGROUND OF THE INVENTION

Numerous applications exist in industry where it is desirable andnecessary in some cases to provide protective and/or aesthetic featuresto a surface. Such applications include use of a paintable sealer forautomobile bodies. Historically, a variety of materials have been usedas sealers to fill voids in structures and exclude dirt, moisture, andother materials.

Sealers have been supplied as liquids or solids depending upon thedemands of the application. In the automotive industry, paste-likeplastisols have been used for decades to seal metal seams, as describedin U.S. Pat. No. 4,900,771 (Gerace et al.). These materials function byhaving PVC (polyvinyl chloride) particles swell in a plasticizer whenheated, and fuse into a solid material. Typically, paint adheres poorlyto PVC based sealers due to the high levels of plasticizer. In addition,PVC sealers cannot be recycled, and when burned, give off HCl. For thisreason they are not used in Europe.

Hot melt sealants and adhesives are generally solid thermoplasticmaterials which quickly melt with heating and then form a firm bond oncooling. A typical class of hot melt adhesive compositions utilizespolyolefins which are known in the art to be difficult to paint andwhich have poor adhesion to non-porous metallic surfaces, such as steeland aluminum.

In use, a bead of the liquid sealer is applied on the joint seam, in theway caulking is applied, and the worker must brush or level the materialout into a relatively uniform film. The application of a liquid sealertakes skill and often results in a poorly sealed seam. Liquid sealerscannot be used for visible applications due to non-uniform appearance.

Recently there has been a trend towards more user-friendly sealersystems such as ropes or tapes because the handling properties of thesematerials make for fast installation and eliminate the need to finessethe material after application. Tapes and ropes of PVC-based sealantmaterial have begun to find niche applications. Other materials havealso been supplied as a strip or tape.

U.S. Pat. No. 3,659,896 (Smith et al.) describes a semi-cured, curablepolymeric sealing strip composition based on a liquid polysulfidepolymer, for adhering and sealing a windshield to an automobile body.The sealing strip has adhesion to both the glass and metal such that thewindshield is immediately sealed at room temperature; further cure ofthe sealant material occurs on exposure to moisture at ambientconditions.

U.S. Pat. No. 4,490,424 (Gerace) describes a hot-melt adhesive andsealant tape in which the tape comprises a core of hot-melt adhesiveencased in a sheath of plastic resin. The plastic resin is compatiblewith the hot-melt adhesive core in both liquid and solid states.

A need exists in industry for a user-friendly, paintable, meltablesealant material that can be used for visible and non-visibleapplications and handled as a strip or tape.

Thermosettable pressure-sensitive adhesives are known and have utilityin a number of industries including assembly of automobiles andappliances. Such adhesives are described in U.S. Pat. No. 5,086,088(Kitano et al.). These adhesives are pressure-sensitive, i.e., tacky atthe temperature of bonding, and are typically used in the form of apressure-sensitive adhesive transfer tape in which the layer of adhesiveis provided on a release liner. The transfer tape can further include anonwoven web for reinforcement of the adhesive layer. In use, thetransfer tape bonds one surface to another surface at ambienttemperature. The surfaces are then heated to a temperature sufficient tocure the adhesive to a thermoset state.

In some applications it would be desirable to have a thermosettablepressure-sensitive adhesive tape that has a non-tacky surface that canbe activated to an adhesive state at the temperature of use.

One such application is in some automotive assembly lines where thedoors are temporarily attached to the vehicle body by bolting the hingeson to the body prior to painting. The door is positioned on the vehicleby aligning the door hinges on slotted holes in the car body, and thenfastening the hinges to the body with one or more washers andcorresponding bolts. After the vehicle body has been painted, the doorsare removed from the hinges so that interior parts can be installed. Itwould be desirable to have the washers fixed in place on the hinges sothat when the doors are re-attached, they will be precisely alignedwithout having to take time to re-align them.

Japanese Patent Publication (Kokai) No. 64-67417 describes a washerfixed to a door hinge with a tacky thermosetting adhesive film. Thewasher serves as an alignment member for a bolt that is used to join thehinge to a door. The film is tacky on both sides and is prone tocontamination from dust, oil, etc., which can be found in assemblyplants. The contaminated surface, in turn, must be cleaned to ensure anadequate bond. The film also tends to be very thin so that it can bedifficult to handle, and removing the liners so that the film can bebonded to the washers and the bolted surfaces can be a labor intensiveoperation which prohibits automation of the assembly line.

It is known to saturate a nonwoven fabric as a support with athermosettable adhesive to increase the rigidity of the adhesive so thatit can be handled more easily, but this would add cost and does not getaround the other deficiencies of the above-described adhesive film.

Japanese Patent Publication (Kokai) No. 53-42280 describes a compositesheet having a sheet of thermosetting material that is coated with aheat fusing material. The heat fusing material is intended to coat thethermosetting resin sheet so that workers can avoid direct skin contactwith the thermosetting adhesive. The thermosetting material and the heatfusing material are mutually non-reactive and compatible, andcharacterized by a maximum difference in fusing temperatures of 50° C.The heat fusing material melts and mixes with the thermosetting materialbefore it is hardened.

Japanese Laid-Open Patent Application JP H4-189885 describes athermosettable pressure-sensitive adhesive made from acrylate copolymersand epoxy resin. The adhesive composition can be coated onto one or bothsides of a nonwoven material, which acts as a pre-preg to increase thestrength of the adhesive sheet.

It would be desirable to have a thermosettable pressure-sensitiveadhesive tape that is substantially tack-free at room temperature (about21° C.) on at least one major surface, but both major surfaces of thetape can be adapted for bonding to other substrates.

SUMMARY OF THE INVENTION

The invention provides an adhesive composite comprising a layer ofthermosettable pressure-sensitive adhesive and a layer of hot meltadhesive that is substantially tack-free at room temperature.Preferably, the hot melt adhesive has a heat activation temperature offrom about 50° C. to the temperature used to cure the thermosettableadhesive.

The invention also provides an adhesive composite for bonding to awasher which will bond to the washer at ambient temperature, and forfurther bonding of the washer to a surface after a heating cycle, and awasher bonded with the composite.

The invention also provides a method for bonding the composite towashers.

The invention further provides a hot melt sealing tape and a method forusing the tape.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the methods and articles particularly pointed out in thewritten description and claims hereof.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tothe accompanying drawings, in which:

FIG. 1a is a cross-sectional view showing a sheet material according tothe invention situated in an automobile roof ditch prior to heating.

FIG. 1b is a cross-sectional view showing the sheet material shown inFIG. 1a after heating.

FIG. 2 is a cross-sectional view of a two-layer sheet material accordingto the invention.

FIG. 3a is a cross-sectional view of another two-layer sheet materialaccording to the invention.

FIG. 3b is a cross-sectional view showing the sheet material of FIG. 3asituated in an automobile roof ditch prior to heating.

FIG. 3c is a cross-sectional view showing the sheet material of FIG. 3asituated in an automobile roof ditch after heating.

FIG. 4a is a top view of a washer having a sheet material of theinvention adhered thereto.

FIG. 4b is a cross-sectional view along the line 4b of FIG. 4a.

FIG. 4c is a sectional view showing the embodiment of FIG. 4a having abolt inserted therein for joining a door hinge to a door frame.

FIGS. 5a and 5b are referred to in Examples 22 and 23.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises the use of a melt-flowable sheetmaterial to provide protective and/or aesthetically pleasing features toa substrate. Generally, the method of the invention includes placing amelt-flowable sheet material over the substrate and heating the sheetmaterial to cause sufficient softening of the sheet material so that itbonds to the substrate. When the melt-flowable sheet is placed on thesubstrate at room temperature, it is substantially tack-free. As thesheet is heated, it first softens and conforms to the surface of thesubstrate, thereby allowing trapped air to be pushed out by the flowingmaterial. Further into the heating cycle, as the sheet material becomeshotter, it becomes tacky, and wets out sufficiently on the surface tobond to the surface. In some applications, the sheet material will alsomelt and flow to conceal defects, surface imperfections, and/or fill ingaps.

After the sheet has been bonded to the surface, the sheet material mayremain melt-flowable, i.e., thermoplastic, wherein re-heating will causethe material to flow again; the sheet material may cure or cross-linkwhen it is heated and become thermoset so that it no longer flows whenre-heated; or a portion of the sheet material may cure or becomecross-linked, i.e., thermoset, while a portion of the sheet materialremains thermoplastic.

The method of the present invention has a number of applications inindustry. One utility of the method is in the automotive industry whereit can be utilized in a process to seal metal joints in automobiles. Bythis process, one first prepares the sheet material such as by theabove-described process. Subsequently, the sheet material would beapplied over the joint to be sealed. Complete sealing and bonding wouldbe obtained because the sheet material flows prior to hardening. As aresult of the controlled flow of the edges of the sheet material, anaesthetic surface appearance is achieved. The exposed surface of thehardened sheet material can then be painted or otherwise decorated tomatch the automobile body.

An alternative application of the method of the invention is in theapplication of emblems or insignia or design elements to surfaces suchas an automobile body. An example of an emblem or insignia is a logo ofan automobile manufacturer. An example of a design element is trim toenhance and highlight auto body curvature and to provide protection tothe primed metal substructure without the need for complex metalstamping to obtain the shape. In such a method, the sheet material isconfigured initially in the shape of the emblem or insignia or designelements desired such as by die-cutting. Practice of the method of theinvention thereby provides an aesthetically pleasing emblem or insigniahaving smooth transition lines relative to the surface to which it hasbeen bonded.

In still another application of the method of the invention, thesubstrate to which the sheet material is initially adhered is atemporary substrate such as a disposable liner. Subsequent to hardeningof the sheet material in a fashion to provide the controlled flow of itsedges, the hardened sheet material may be fastened (e.g., adhered) tothe permanent substrate through the use, for example, of an adhesivesystem distinct from the sheet material itself since the hardened sheetmaterial may be substantially devoid of pressure-sensitive adhesiveproperties. In this manner, the method of the invention may be used toapply configured, hardened sheet materials such as signs to surfacessuch as wooden doors.

The melt-flowable sheet material can be placed in a roof ditch on anautomobile before it is painted to conceal unsightly flaws in the metal,spot welds, and the step joint where the sheet metal of the roof iswelded to the sheet metal of the car body.

In one specific embodiment, the melt-flowable sheet material is cut intoa strip having a width slightly greater than the width of the roof ditchand a length equal to the length of the ditch. The roof ditch may beunprimed, unprimed with a portion sealed with conventional sealers,primed with conventional primers, or primed and painted. Typically, theautomobile would be primed with an electrodeposition coating as detailedhereinbelow prior to application of the strip. The strip is then heatedin the ditch so the strip material flows and levels out over anyimperfections and the step joint in the roof ditch creating a smooth,aesthetically pleasing appearance within the ditch. At the same time,the melt-flowable strip also adheres to the inside surfaces of the roofditch and provides a protective seal in the ditch to prevent rain water,dirt, snow, etc. from getting into the roof ditch and causing rusting orcorrosion. In this application, in which the strip has a width slightlygreater than the width of the roof ditch, the strip material also takeson a concave configuration along the length of the roof ditch to providea channel to carry water off the roof of the car.

The strip material is preferably compatible with the paint and allowsthe paint to dry and cure without wrinkling or cracking of the paint,while bonding tightly to both the paint and the surfaces of the roofditch.

The automobile, with the strip in place, may then be painted and putthrough an oven cure cycle at about 170° C. for about 20 minutes. Aprotective clear coat may also be applied and cured. It is recognizedthat the oven cure times and temperatures will vary depending upon thepaint line, and the paint and clear coat cure requirements. Typicalcycles can range from about 20 to 40 minutes at temperatures betweenabout 120° C. and 200° C.

In a preferred embodiment, the paint also reacts chemically with themelt-flowable strip material to improve the adhesion between the paintand the melt-flowable strip. The reaction of the paint with the stripmaterial causes the strip material to become thermoset at, and near, theinterface of the strip with the paint, while the strip material remainsthermoplastic below the interfacial layer.

In another preferred embodiment, the melt-flowable strip itself is athermosettable material which reacts with the paint during the curecycle, and also undergoes curing to provide a strip that is thermoset.The curing may be achieved by thermal or radiation means as is discussedhereinbelow.

In an alternative embodiment, the strip may be placed in the roof ditchafter the automobile has been painted. The roof ditch area can then beheated with conventional heaters, such as an infrared heater or a quartzhalogen lamp, to melt and bond the strip to the roof ditch withoutfurther processing. In this embodiment, the strip may be compounded withpigments to provide a contrasting or complementary color. The meltsealing strip material may remain thermoplastic, become thermosetthroughout the thickness of the strip, or become thermoset only at thesurface of the strip.

The melt-flowable sheet materials are preferably solid, and may or maynot be tacky at room temperature. In some embodiments, the melt sealingsheet material will also function as a hot melt adhesive. Hot meltadhesive materials preferably have a melting point above about 50° C. Asused herein, a "hot melt adhesive composition" refers to a compositionthat is solid and non-tacky at room temperature (about 21° C.) butwhich, upon heating, melts sufficiently to wet out on a surface andadhere to it. Adhesives having melt temperatures below 50° C. may meltprematurely in storage in hot climates and may not perform well inapplications that require a part to be die-cut or punched out on apunch-press as described below.

The sheet material may be formed into a sheet using conventional sheetforming techniques, including extruding the material from a heated die;heating the sheet material to a suitable melt temperature and knifecoating onto a release liner; curtain coating the molten material; ordispersing the material in a solvent, coating onto a release liner, anddrying the solvent. For environmental reasons, the preferred methods aresolvent free systems.

The thickness of the melt-flowable sheet material will vary dependingupon its intended end use. For sealing applications, it is desirable tohave the sheet thick enough to provide sufficient material to flow andlevel out over dents, bumps, and other surface imperfections or to fillin gaps between joints. Useful thicknesses have been found to be in therange of about 0.05 mm (millimeters) to 25 mm. For typical melt sealingapplications where a protective seal is desired, thicknesses may rangefrom 0.10 to 25 mm, preferably 0.20 to 10 mm, and more preferably 0.34to 6 mm.

The melt-flowable sheet material can be packaged in the form of rolls ofsheet material, rolls of tapes, i.e., lengths of material in narrowwidths, or stacks of sheets cut to a desired dimension or shape for theend use. If the compositions of the melt-flowable sheet material aretacky, a release liner may be interleaved between adjacent sheets orwraps of a roll. In some two layer sheet constructions in which onelayer is tacky, the non-tacky layer may serve as the liner withoutrequiring a separate liner. If the sheet material includes a latentlight activated catalyst in the sheet, the sheet is preferably packagedand transported in the absence of actinic radiation, until ready foruse.

The compositions for the melt-flowable sheet material can also bepackaged for use in a hot-melt applicator system with the use of pailunloaders, cartridge dispensers, and the like. The compositions can thenbe heated at the point of use and applied in the molten state to thesubstrate. This method may require specialized equipment to apply thecomposition.

The melt-flowable materials can be applied and bonded to most substratesincluding plastics, metals, ceramics, glass, and cellulosic materials;primed, bare, or painted metal substrates such as aluminum, cold rolledsteel, galvanized steel, and porcelainized steel are particularlypreferred.

The melt-flowable sheet can include one or more other layers for variouspurposes as detailed hereinbelow. Such layers include a thermosettablemelt sealing layer, a thermosettable pressure-sensitive adhesive layer,a pressure-sensitive adhesive layer, a second melt-flowable layer, e.g.,one having a different glass transition temperature than the firstmelt-flowable layer, a layer capable of cross-linking with themelt-flowable layer at the interface between the two layers, anexpandable layer, a nonwoven layer, or a polymeric film, e.g., athermoplastic film that is preferably dimensionally stable at thetemperatures of application and use. Various methods of bonding theadditional layers to the melt-flowable layer include techniques known inindustry such as heat lamination, bonding with a pressure-sensitiveadhesive, co-extruding the second layer with the melt-flowable layer,hot melt coating, direct coating of the second layer to the first, andthe like.

The melt-flowable sheet material useful in the practice of the inventioncomprises thermoplastic polymeric materials that have functional groupsthat can react with typical paints used in the industry such as thosebased on melamine or epoxy.

Preferred thermoplastic polymers are functionalized amorphous orsemi-crystalline polymers having a glass transition temperature above-30° C. and functionalized semi-crystalline polymers having a glasstransition temperature below -30° C. Useful polymers are those havingfunctional groups including --OH, --NH, --CONH, --COOH, --NH₂, --SH,anhydrides, urethanes, and oxirane. Preferred functional groups are--OH, --COOH, and --NH. Examples of useful polymers include polyesters,polyamides, functionalized ethylene (meth)acrylates, such as thosefunctionalized with --OH groups, ethylene acrylic acids, polysulfides,polyacetals, such as polyvinylbutyral, olefinic polymers having theappropriate functional groups, such as ethylene-(meth)acrylic acid,propylene-(meth)acrylic acid, ethylene-(meth)acrylic ester,propylene-(meth)acrylic ester, polycaprolactones, epoxy polycaprolactonecompositions, and epoxy polyester hot melt compositions described in theparent application, U.S. Ser. No. 08/047,862, filed Apr. 15, 1993, andcompatible blends thereof.

Preferred materials for the melt-flowable sheet material includepolycaprolactones, and polyesters having hydroxyl and carboxyltermination and may be amorphous or semi-crystalline at roomtemperature. More preferred are hydroxyl terminated polyesters that aresemi-crystalline at room temperature. A material that is "amorphous" hasa glass transition temperature but does not display a measurablecrystalline melting point as determined on a differential scanningcalorimeter (DSC). Preferably, the glass transition temperature is lessthan the decomposition temperature of a photoinitiator, if one is usedas described hereinbelow, but without being more than about 120° C. Amaterial that is "semi-crystalline" displays a crystalline melting pointas determined by DSC, preferably with a maximum melting point of about200° C.

Crystallinity in a polymer is also observed as a clouding or opacifyingof a sheet that had been heated to an amorphous state as it cools. Whenthe polyester polymer is heated to a molten state and knife coated ontoa liner to form a sheet, it is amorphous and the sheet is observed to beclear and fairly transparent to light. As the polymer in the sheetmaterial cools, crystalline domains form and the crystallization ischaracterized by the clouding of the sheet to a translucent or opaquestate. The degree of crystallinity may be varied in the polymers bymixing in any compatible combination of amorphous polymers andsemi-crystalline polymers having varying degrees of crystallinity. It isgenerally preferred that material heated to an amorphous state beallowed sufficient time to return to its semi-crystalline state beforepainting so that the paint is applied to a uniformly consistent surface.The clouding of the sheet provides a convenient non-destructive methodof determining that crystallization has occurred to some degree in thepolymer.

The polymers may include nucleating agents to increase the rate ofcrystallization at a given temperature. Useful nucleating agents includemicrocrystalline waxes. A suitable wax is one comprising C greater than14 (CAS #71770-71-5) alcohol and an ethylene homopolymer (CAS#9002-88-4) sold by Petrolite Corp. as Unilin 700. Paint catalysts suchas para-toluene sulfonic acid may be added to the polyester, as well asmelamines to improve the adhesion of the melt-flowable layer to paintand coatings.

The preferred polyesters are solid at room temperature. Preferredpolyester materials have a number average molecular weight of about 7500to 200,000, more preferably from about 10,000 to 50,000, and mostpreferably, from about 15,000 to 30,000.

Polyester components useful in the invention comprise the reactionproduct of dicarboxylic acids (or their diester equivalents) and diols.The diacids (or diester equivalents) can be saturated aliphatic acidscontaining from 4 to 12 carbon atoms (including branched, unbranched, orcyclic materials having 5 to 6 carbon atoms in a ring) and/or aromaticacids containing from 8 to 15 carbon atoms. Examples of suitablealiphatic acids are succinic, glutaric, adipic, pimelic, suberic,azelaic, sebacic, 1,12-dodecanedioic, 1,4-cyclohexanedicarboxylic,1,3-cyclopentanedicarboxylic, 2-methylsuccinic, 2-methylpentanedioic,3-methylhexanedioic acids, and the like. Suitable aromatic acids includeterephthalic acid, isophthalic acid, phthalic acid, 4,4'-benzophenonedicarboxylic acid, 4,4'-diphenylmethanedicarboxylic acid,4,4'-diphenylthioether dicarboxylic acid, and 4,4'-diphenylaminedicarboxylic acid. Preferably the structure between the two carboxylgroups in the diacids contain only carbon and hydrogen, and morepreferably, the structure is a phenylene group. Blends of the foregoingdiacids may be used.

The diols include branched, unbranched, and cyclic aliphatic diolshaving from 2 to 12 carbon atoms. Examples of suitable diols includeethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol,1,4-butanediol, 1,3-butanediol, 1,5-pentanediol,2-methyl-2,4-pentanediol, 1,6-hexanediol,cyclobutane-1,3-di(2'-ethanol), cyclohexane-1,4-dimethanol,1,10-decanediol, 1,12-dodecaniediol, and neopentyl glycol. Long chaindiols including poly(oxyalkylene)glycols in which the alkylene groupcontains from 2 to 9 carbon atoms, preferably 2 to 4 carbon atoms, mayalso be used. Blends of the foregoing diols may be used.

Useful, commercially available hydroxyl terminated polyester materialsinclude various saturated linear, semi-crystalline copolyestersavailable from Huls America, Inc. such as Dynapol™S1401, Dynapol™S1402,Dynapol™S1358, Dynapol™S1359, Dynapol™S1227, and Dynapol™S1229. Usefulsaturated, linear amorphous copolyesters available from Huls America,Inc., include Dynapol™S1313 and Dynapol™S1430.

The foregoing polyesters may be cast into sheets by melting thepolyester resin at temperatures from about 100° to 150° C. to form amolten material and knife coating onto a liner such as a siliconerelease coated paper. The polyester materials may further includefillers as detailed below for an epoxy polyester composition.

Sheets formed from the foregoing polyesters are particularly useful forsealing and bonding to surfaces having gaps and imperfections such as inthe above described roof ditch molding on an automobile. In addition,these polyesters have been found to provide paint compatible surfacesfor melamine and epoxy paints and will withstand at least two typicalpaint curing cycles (e.g., 20-30 minutes at 120° C., and 20-30 minutesat 200° C.). It has also been found that these polyesters, when coatedwith epoxy and melamine paints, will react with the paint at theinterface between the melt-flowable sheet and the paint.

Also preferred for the melt-flowable sheet material are epoxypolycaprolactone compositions and epoxy polyester hot melt compositions.Polycaprolactones are biodegradable in soil. Especially preferred areepoxy polyester hot melt compositions which cure on exposure toradiation to provide high strength sealing materials having goodadhesion to the substrate to which it is adhered. The epoxy-containingmaterial contributes to the ultimate strength and heat resistance of thecomposition, while the polyester component allows the sheet material toconform to the substrate and provides initial adhesion to the substrate,and the photoinitiator permits the composition to cure (i.e., covalentlycross-link) upon exposure to radiation. Optionally, the hot meltcompositions of the invention may also include a hydroxyl-containingmaterial to impart flexibility and toughness to the hot meltcompositions. Preferred polyesters for the epoxy/polyester sheetmaterial are those hydroxyl and carboxyl terminated functional materialsdescribed above. Especially preferred are hydroxyl terminated polyestershaving some degree of crystallinity.

Epoxy-containing materials useful in the compositions of the inventionare any organic compounds having at least one oxirane ring ##STR1##polymerizable by a ring opening reaction. Such materials, broadly calledepoxides, include both monomeric and polymeric epoxides and can bealiphatic, cycloaliphatic, or aromatic. These materials generally have,on the average, at least two epoxy groups per molecule (preferably morethan two epoxy groups per molecule). The "average" number of epoxygroups per molecule is defined as the number of epoxy groups in theepoxy-containing material divided by the total number of epoxy moleculespresent. The polymeric epoxides include linear polymers having terminalepoxy groups (e.g., a diglycidyl ether of a polyoxyalkylene glycol),polymers having skeletal oxirane units (e.g., polybutadienepolyepoxide), and polymers having pendent epoxy groups (e.g., a glycidylmethacrylate polymer or copolymer). The molecular weight of theepoxy-containing material may vary from 58 to about 100,000 or more.Mixtures of various epoxy-containing materials can also be used in thehot melt compositions of the invention.

Useful epoxy-containing materials include those which containcyclohexene oxide groups such as the epoxycyclohexanecarboxylates,typified by 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate,3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate. For amore detailed list of useful epoxides of this nature, reference may bemade to U.S. Pat. No. 3,117,099.

Further epoxy-containing materials which are particularly useful in thepractice of this invention include glycidyl ether monomers of theformula ##STR2## where R' is alkyl or aryl and n is an integer of 1 to6. Examples are the glycidyl ethers of polyhydric phenols obtained byreacting a polyhydric phenol with an excess of chlorohydrin such asepichlorohydrin (e.g., the diglycidyl ether of2,2-bis-(2,3-epoxypropoxyphenol) propane). Further examples of epoxidesof this type which can be used in the practice of this invention aredescribed in U.S. Pat. No. 3,018,262.

There is a host of commercially available epoxy-containing materialswhich can be used in this invention. In particular, epoxides which arereadily available include octadecylene oxide, epichlorohydrin, styreneoxide, vinyl cyclohexene oxide, glycidol, glycidylmethacrylate,diglycidyl ether of Bisphenol A (e.g., those available under the tradedesignations EPON 828, EPON 1004, and EPON 1001F from Shell ChemicalCo., and DER-332 and DER-334, from Dow Chemical Co.), diglycidyl etherof Bisphenol F (e.g., ARALDITE GY281 from Ciba-Geigy), vinylcyclohexenedioxide (e.g., ERL 4206 from Union Carbide Corp.),3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate (e.g.,ERL4221 from Union Carbide Corp.),2-(3,4-epoxycylohexyl-5,5-spiro-3,4-epoxy) cyclohexanemetadioxane (e.g.,ERL-4234 from Union Carbide Corp.), bis(3,4-epoxycylohexyl) adipate(e.g., ERL-4299 from Union Carbide Corp.), dipentene dioxide (e.g.,ERL-4269 from Union Carbide Corp.), epoxidized polybutadiene (e.g.,OXIRON 2001 from FMC Corp.), silicone resin containing epoxyfunctionality, epoxy silanes (e.g.,beta-(3,4-epoxycyclohexyl)ethyltrimethoxy silane andgamma-glycidoxypropyltrimethoxy silane, commercially available fromUnion Carbide), flame retardant epoxy resins (e.g., DER-542, abrominated bisphenol type epoxy resin available from Dow Chemical Co.),1,4-butanediol diglycidyl ether (e.g., ARALDITE RD-2 from Ciba-Geigy),hydrogenated bisphenol A-epichlorohydrin based epoxy resins (e.g.,EPONEX 1510 from Shell Chemical Co.), and polyglycidyl ether ofphenolformaldehyde novolak (e.g., DEN-431 and DEN-438 from Dow ChemicalCo.).

The photoinitiators which are useful in the compositions of theinvention are cationic and include these three types, viz. aromaticiodonium complex salts, aromatic sulfonium complex salts and metallocenesalts. Useful aromatic iodonium complex salts have the formula: ##STR3##where Ar¹ and Ar² are aromatic groups having 4 to 20 carbon atoms andare selected from the group consisting of phenyl, thienyl, furanyl, andpyrazolyl groups. Z is selected from the group consisting of oxygen;sulfur; ##STR4## where R is aryl (of 6 to 20 carbons, such as phenyl) oracyl (of 2 to 20 carbons, such as acetyl, benzoyl, etc.); acarbon-to-carbon bond; or ##STR5## where R₁ and R₂ are selected fromhydrogen, alkyl radicals of 1 to 4 carbons, and alkenyl radicals of 2 to4 carbons. The value of m is zero or 1 and X is a halogen-containingcomplex anion selected from tetrafluoroborate, hexafluorophosphate,pentafluorohydroxyantimonate, hexafluoroarsenate, andhexafluoroantimonate.

The Ar¹ and Ar² aromatic groups may optionally have one or more fusedbenzo rings (e.g., naphthyl, benzothienyl, dibenzothienyl, benzofuranyl,dibenzofuranyl, etc.). The aromatic groups may also be substituted, ifdesired, by one or more non-basic groups if they are essentiallynon-reactive with epoxide and hydroxyl functionalities.

Useful aromatic iodonium complex salts are described more fully in U.S.Pat. No. 4,256,828. The preferred aromatic iodonium complex salts arediaryliodonium hexafluorophosphate and diaryliodoniumhexafluoroantimonate.

The aromatic iodonium complex salts useful in the compositions of theinvention are photosensitive only in the ultraviolet region of thespectrum. They, however, can be sensitized to the near ultraviolet andthe visible range of the spectrum by sensitizers for known photolyzableorganic halogen compounds. Illustrative sensitizers include aromaticamines and colored aromatic polycyclic hydrocarbons.

Aromatic sulfonium complex salt photoinitiators suitable for use in thecompositions of the invention can be defined by the formula ##STR6##wherein R₃, R₄ and R₅ can be the same or different, provided that atleast one of the groups is aromatic. These groups can be selected fromaromatic moieties having 4 to 20 carbon atoms (e.g., substituted andunsubstituted phenyl, thienyl, and furanyl) and alkyl radicals having 1to 20 carbon atoms. The term "alkyl" includes substituted alkyl radicals(for example, substituents such as halogen, hydroxy, alkoxy, aryl).Preferably, R₃, R₄ and R₅ are each aromatic. Z, m and X are all asdefined above with regard to the iodonium complex salts.

If R₃, R₄ or R₅ is an aromatic group, it may optionally have one or morefused benzo rings (e.g., naphthyl, benzothienyl, dibenzothienyl,benzofuranyl, dibenzofuranyl, etc.) Such aromatic groups may also besubstituted, if desired, by one or more non-basic groups that areessentially non-reactive with epoxide and hydroxyl functionality.

The triaryl-substituted salts such as triphenylsulfoniumhexafluoroantimonate are preferred. Useful sulfonium complex salts aredescribed more fully in U.S. Pat. No. 4,256,828.

The aromatic sulfonium complex salts useful in the invention areinherently photosensitive only in the ultraviolet region of thespectrum. They, however, are sensitized to the near ultraviolet and thevisible range of the spectrum by a select group of sensitizers such asdescribed in U.S. Pat. No. 4,256,828.

Useful metallocene salts can have the formula: ##STR7## wherein M^(P)represents a metal selected from Cr, Mo, W, Mn, Re, Fe, and Co;

L¹ represents 1 or 2 ligands contributing p-electrons that can be thesame or different ligand selected from substituted and unsubstituted h³-allyl, h⁵ -cyclopentadienyl, and h⁷ -cycloheptatrienyl and h⁶ -aromaticcompounds selected from h⁶ -benzene and substituted h⁶ -benzenecompounds and compounds having 2 to 4 fused rings each capable ofcontributing 3 to 8 p-electrons to the valence shell of M^(P) ;

L² represents none or 1 to 3 ligands contributing an even number ofsigma-electrons that can be the same or different ligand selected fromcarbon monoxide or nitrosonium;

with the proviso that the total electronic charge contributed to M^(P)by L¹ and L² plus the ionic charge on the metal M^(P) results in a netresidual positive charge of q to the complex, and

q is an integer having a value of 1 or 2, the residual electrical chargeof the complex cation;

Y is a halogen-containing complex anion selected from AsF₆ --, SbF₆ --and SbF₅ OH--; and

r is an integer having a value of 1 or 2, the numbers of complex anionsrequired to neutralize the charge q on the complex cation.

Useful metallocene salts are described more fully in U.S. Pat. No.5,089,536 (Palazzotto et al.). An example of a useful salt is (η⁵-cyclopentadienyl)(η⁶ -xylenes)Fe⁺ SbF₆ ⁻, also denoted asCp(xylenes)Fe⁺ SbF₆ ⁻. Useful amounts of the metallocene catalyst rangefrom about 0.05 to 20 parts by weight of the epoxy resin, preferablyfrom about 0.07 to about 10 parts, and more preferably from about 0.09to about 3 parts. The metallocene salts may be used in conjunction witha reaction accelerator such as an oxalate ester of a tertiary alcohol.

Useful commercially available photoinitiators include FX-512, anaromatic sulfonium complex salt (3M Company), an aromatic sulfoniumcomplex salt (Union Carbide Corp.), UVI-6974, an aromatic sulfoniumcomplex salt (Union Carbide Corp.), and IRGACURE™261, a metallocenecomplex salt (Ciba-Geigy).

Optionally, the hot melt compositions of the invention may furthercomprise a hydroxyl-containing material. The hydroxyl-containingmaterial may be any liquid or solid organic material having hydroxylfunctionality of at least 1, preferably at least 2, and most preferablyabout 3. The hydroxyl-containing organic material should be free ofother "active hydrogen" containing groups such as amino and mercaptomoieties. The hydroxyl-containing organic material should also besubstantially free of groups which may be thermally or photolyticallyunstable so that the material will not decompose or liberate volatilecomponents at temperatures below about 100° C. or when exposed toactinic or electron beam radiation during curing.

Preferably the organic material contains two or more primary orsecondary aliphatic hydroxyl groups (i.e., the hydroxyl group is bondeddirectly to a non-aromatic carbon atom). The hydroxyl group may beterminally situated, or may be pendent from a polymer or copolymer. Thenumber average equivalent weight of the hydroxyl-containing material ispreferably about 31 to 2250, more preferably about 80 to 1000, and mostpreferably about 80 to 350.

Representative examples of suitable organic materials having a hydroxylfunctionality of 1 include alkanols, monoalkyl ethers of polyoxyalkyleneglycols, and monoalkyl ethers of alkylene glycols.

Representative examples of useful monomeric polyhydroxy organicmaterials include alkylene glycols (e.g., 1,2-ethanediol,1,3-propanediol, 1,4-butanediol, 2-ethyl-1,6-hexanediol,bis(hydroxymethyl)cyclohexane, 1,18-dihydroxyoctadecane, and3-chloro-1,2-propanediol), polyhydroxyalkanes (e.g., glycerine,trimethylolethane, pentaerythritol, and sorbitol) and other polyhydroxycompounds such as N,N-bis(hydroxyethyl)benzamide, 2-butene-1,4-diol,castor oil, etc.

Representative examples of useful polymeric hydroxyl-containingmaterials include polyoxyalkylene polyols (e.g., polyoxyethylene andpolyoxypropylene glycols and triols of equivalent weight of 31 to 2250for the diols or 80 to 350 for triols), polytetramethylene oxide glycolsof varying molecular weight, hydroxyl-terminated polyesters, andhydroxyl-terminated polylactones.

Useful commercially available hydroxyl-containing materials include thePOLYMEG series (available from QO Chemicals, Inc.) of polytetramethyleneoxide glycols such as POLYMEG 650, 1000 and 2000; the TERATHANE series(from E.I. duPont de Nemours and Company) of polytetramethylene oxideglycols such as TERATHANE 650, 1000 and 2000; POLYTHF, apolytetramethylene oxide glycol from BASF Corp.; the BUTVAR series(available from Monsanto Chemical Company) of polyvinylacetal resinssuch as BUTVAR B-72A, B-73, B-76, B-90 and B-98; the TONE series(available from Union Carbide) of polycaprolactone polyols such as TONE0200, 0210, 0230, 0240, and 0260; the DESMOPHEN series (available fromMiles Inc.) of saturated polyester polyols such as DESMOPHEN 2000, 2500,2501, 2001KS, 2502, 2505, 1700, 1800, and 2504; the RUCOFLEX series(available from Ruco Corp.) of saturated polyester polyols such asS-107, S-109, S-1011 and S-1014; VORANOL 234-630 (a trimethylol propane)from Dow Chemical Company; VORANOL 230-238 (a glycerol polypropyleneoxide adduct) from Dow Chemical Company; the SYNFAC series (fromMilliken Chemical) of polyoxyalkylated bisphenol A's such as SYNFAC8009, 773240, 8024, 8027, 8026, and 8031; and the ARCOL series (fromArco Chemical Co.) of polyoxypropylene polyols such as ARCOL 425, 1025,2025, 42, 112, 168, and 240.

The amount of hydroxyl-containing organic material used in thecompositions of the invention may vary over a broad range, depending onfactors such as the compatibility of the hydroxyl-containing materialwith both the epoxy-containing material and the polyester component, theequivalent weight and functionality of the hydroxyl-containing material,and the physical properties desired in the final cured composition.

The optional hydroxyl-containing material is particularly useful intailoring the flexibility of the hot melt compositions of the invention.As the equivalent weight of the hydroxyl-containing material increases,the flexibility of the hot melt composition correspondingly increasesalthough there may be a consequent loss in cohesive strength. Similarly,decreasing equivalent weight may result in a loss of flexibility with aconsequent increase in cohesive strength. Thus, the equivalent weight ofthe hydroxyl-containing material is selected so as to balance these twoproperties, the appropriate balance depending on the particularapplication.

Flexible melt sealing compositions are useful in forming flexible sheetsfor sealing performance at lower temperatures, i.e., below about 0° C.If the hydroxyl-containing material is used to tailor the flexibility ofthe melt sealing composition, polyoxyethylene glycols and triols havingan equivalent weight of about 31 to 2250 for the glycols and 80 to 350for the triols are particularly preferred. Even more preferred arepolyoxypropylene glycols and triols having an equivalent weight of about31 to 2250 for the glycols and an equivalent weight of about 80 to 350for the triols.

The melt-flowable compositions of the invention comprise from 0.01 to 95parts per 100 parts total of the epoxy-containing material and,correspondingly, from 99.99 to 5 parts of the polyester component. Morepreferably, the melt-flowable compositions of the invention comprisefrom 0.1 to 80 parts of the epoxy-containing material and,correspondingly, from 99.9 to 20 parts of the polyester component. Mostpreferably, the hot melt compositions of the invention comprise from 0.5to 60 parts of the epoxy-containing material, and, correspondingly, from99.5 to 40 parts of the polyester component. Increasing amounts of theepoxy-containing material relative to the polyester component generallyresult in melt-flowable compositions having higher ultimate strength andheat resistance but less flexibility, and lower viscosity. Increasingamounts of the polyester component generally result in melt-flowablecompositions having lower ultimate strength, heat resistance and higherviscosity but greater flexibility and green strength build-up. Thus, therelative amounts of these two ingredients are balanced depending on theproperties sought in the final composition.

The photoinitiator, if used, is included in an amount ranging from about0.01 to 4% based on the combined weight of the epoxy-containing materialand the polyester component. Increasing amounts of the photoinitiatorcan result in an accelerated curing rate. Increased amounts ofphotoinitiator can also result in reduced energy exposure requirements.The amount of the photoinitiator is determined by the rate at which thecomposition should cure, the intensity of the radiation source, and thethickness of the composition.

In some applications, it is useful to initially radiation cure themelt-flowable composition only at the surface of the sheet, andsubsequently thermally cure the entire sheet later. For example, anactinic radiation curable epoxy polyester sheet material is exposed toactinic radiation to cure the surface of the sheet material, and thenplaced in the aforementioned roof ditch such that the sheet materialforms a concave surface along the roof ditch as shown in FIG. 1b. Thestrip is then heated to a temperature sufficient to bond the strip tothe surfaces within the ditch, and cure the entire thickness of thesheet. The result is a skinned surface on the sheet material that aidsin providing a smooth surface for visual and functional reasons.

Melt-flowable compositions which include a polyether polyol may beuseful in allowing the melt-flowable sheet to conform to the surface anddisplace trapped air before forming a permanent bond to the substrate.

Additionally, and optionally, up to 50% of the total volume of thecomposition (based on the epoxy-containing material, the polyestercomponent, the photoinitiator and the optional hydroxyl-containingmaterial), may be provided by various fillers, adjuvants, additives andthe like such as silica, glass, clay, talc, pigments, colorants, glassbeads or bubbles, glass or ceramic fibers, antioxidants, and the like soas to reduce the weight or cost of the composition, adjust viscosity,and provide additional reinforcement. Fillers and the like which arecapable of absorbing the radiation used during the curing process shouldbe used in an amount that does not adversely affect the curing process.

The melt-flowable compositions comprising the foregoing polyester andepoxy polyester materials are prepared by mixing the various ingredientsin a suitable vessel, preferably one that is not transparent to actinicradiation if a photoinitiator is used, at an elevated temperaturesufficient to liquefy the components so that they can be efficientlymixed with stirring until the components are thoroughly melt blended butwithout thermally degrading the materials. The components may be addedsimultaneously or sequentially, although it is preferred to first blendthe epoxy-containing material and the polyester component followed bythe addition of the hydroxyl-containing material and then thephotoinitiator. The melt-flowable compositions should be compatible inthe melt phase, i.e., there should be no visible gross phase separationamong the components.

The melt-flowable sheet made with epoxy polyester compositions may betacky or tack-free. A blend of liquid and solid epoxy-containingmaterials is useful in providing a tacky sheet.

In use, the melt-flowable sheet materials containing a photoinitiatorcan be exposed to a radiation source to activate the catalyst for curingof the epoxy-containing material before, during, or after the sheetmaterial has been applied to the substrate. Activation of the catalystoccurs upon exposure of the sheet materials to any source emittingactinic radiation (i.e., radiation having a wavelength in theultraviolet or visible spectral regions). Suitable sources of radiationinclude mercury, xenon, carbon arc, tungsten filament lamps, quartzhalogen lamps, fluorescent lights, sunlight, etc. Exposure times must besufficient to activate the catalyst and may vary from less than about 1second to 20 minutes or more depending upon both the amount and the typeof reactants involved, the radiation source, the distance from theradiation source, and the thickness of the sheet.

The time needed to reach fill cure may be accelerated by curing thesheet materials with heat, such as in an oven. The time and temperatureof the cure will vary depending upon the glass transition temperature ofthe polyester component, the concentration of the photoinitiator, theradiation exposure conditions, and the like. Typical cure cycleconditions range from 5 to 30 minutes with temperatures ranging fromabout 50° C. to 200° C. More than one heating cycle may be used to curethe sheet materials.

The compositions may also be cured by exposure to electron beamradiation. The dosage necessary is generally from less than 1 megarad to100 megarads or more. The rate of curing tends to increase withincreasing amounts of photoinitiator at a given light exposure orirradiation. The rate of curing also increases with increased radiationintensity or electron dosage.

Other layers may be included in the melt-flowable sheet for variouspurposes. A second melt-flowable layer may be adhered to the one majorsurface of the first melt-flowable sheet to improve the topographicaland aesthetic features of a surface.

Furthermore, one or more of the layers of a sheet material of theinvention may include other ingredients disclosed in application U.S.Ser. No. 08/386,251, filed Feb. 9, 1995, continuation of U.S. Ser. No.08/150,212, filed Nov. 10, 1993, both of which are hereby incorporatedby reference. Examples of such ingredients are polyacetals, reinforcingcopolymers, and polycaprolactone diols. Further examples includeglycidyl methacrylate, silanes and other species to provide forcrosslinking between separated polymeric phases.

A second layer may be included in the melt-flowable sheet material toimprove outdoor weatherability of the tape.

The second layer of the melt-flowable tape can include thermal expansionagents such as blowing agents, foaming agents, expandable polymericmicrospheres and the like to impart a convex shape to a surface.

A woven or nonwoven web or scrim may be included in the melt-flowablesheet material. The web can be laminated to the melt-flowable layerusing an adhesive or by heat lamination techniques, and may be insertedbetween two melt-flowable layers. Addition of a nonwoven web has beenfound to be useful in controlling the flow of the melt-flowable layer.The woven or nonwoven web can also be used to impart strength to thesheet material for better handling properties.

Other materials that can be included as part of the melt-flowable sheetmaterial are thermoplastic films. Preferably, the films aredimensionally stable at the temperatures to which they might be exposedto either in applying the melt-flowable sheet material to a substrate,e.g., when the sheet material is heated to a temperature necessary tocause flow and/or thermosetting of the sheet material, or after it hasbeen applied, e.g., exposure to cold weather temperatures, sunlight,etc. Useful films include polyurethane films, oriented polyester films,polyimide films, polyolefin films, and the like. The films can be usedto provide smooth surfaces for painting or as the finished surface afterthe melt-flowable sheet has been bonded to a surface.

Thermoset films can also be used. Examples of thermoset films includefilms made from the above-described epoxy polyester materials that havebeen crosslinked, cross-linked epoxy films, and the like.

Preferred films include films made from the above described epoxypolyester materials, polyester films include polyethylene terephthalatefilms, ultrahigh molecular weight polyethylene films, microporousultrahigh molecular weight polyethylene films, ultrahigh molecularweight polypropylene films, ultrahigh molecular weight microporouspolypropylene films, and polyimide films. Ultrahigh molecular weightpolyolefin films are preferred in some embodiments because the very longchains of these polyolefins can soften upon heating without exhibitingthe molten liquid flow typical of thermoplastic materials.

Useful ultrahigh molecular weight polyethylene films have an intrinsicviscosity of at least about 18 deciliters per gram (dL/g), a typicalrange of intrinsic viscosities between about 18 and 39 dL/g, and apreferred range between 18 and 32 dL/g. Useful ultrahigh molecularweight polypropylene films have an intrinsic viscosity of at least 6dL/g. A typical range of intrinsic viscosities is 6 to about 18 dL/g,and a preferred range is 6 to 16 dL/g.

Both thermoset and thermoplastic films should be dimensionally stable atthe temperatures to which they are exposed. By dimensionally stable, itis meant that at the films have sufficient integrity at the temperaturesof use, and particularly, during the heat curing cycle of the meltsealing layer at about 120C to 200C for 20 to 40 minutes, so they do notmelt and flow. Also the films do not exhibit wrinkling when they areheated to the melt sealing temperature and subsequently cooled. Thefilms also have enough integrity to prevent entrapped air bubbles in themelt sealing layer from blowing through the film and causing a defect.Preferably, the films, after they have been laminated to a melt sealinglayer and heated to the temperature needed to bond the melt sealinglayer to a surface, will exhibit a downweb and crossweb shrinkage ofless than about 5%, more preferably, less than about 3%, and mostpreferably, less than about 2%. In highly preferred embodiments, thefilms will exhibit less than 1% shrinkage in the downweb direction, andless than 0.5% in the crossweb direction.

Depending upon the application, it may be desirable to have a certainamount of shrinkage in the film to help control the flow of theunderlying melt sealing material.

The films can contain additives to improve or impart various propertiessuch as paint adhesion and thermal stability. Useful materials for thesepurposes include siliceous fillers such as silica, talc, zeolites,kaolinite, mica, alumina silica gels, glass, and the like, carbonaceousmaterials, inorganic metal oxides, sulfides, sulfates, and carbonates.Examples include carbon black, iron oxide, titanium oxide, zirconia,zinc sulfide, barium sulfate, calcium carbonate, and magnesiumcarbonate. Preferred fillers are silicas and clays, and preferredsiliceous fillers are precipitated silica, silica gel, and fumed silica.Fillers can be used in amounts from about 5% to 90% by weight based onthe total weight of the film.

In a preferred embodiment, the film is a microporous ultrahigh molecularweight microporous polyolefin film having 50 to 90% by weight of thetotal weight of the film of a siliceous fillers and a network ofinterconnecting pores throughout the film with the pores constituting 35to 80 percent by volume of the film.

Useful commercially available films include microporous films sold byPPG Industries under the Teslin™ tradename, and polyester films sold byICI Americas under the Melinex™tradename.

Suitable microporous films are also described in U.S. Pat. No. 4,861,644(Young et al.) and U.S. Pat. No. 4,439,256 (Shipman), both of which arehereby incorporated by reference.

The dimensionally stable film can be used alone or in combination. Forexample, a suitable construction could include a 0.003 inch thickpolyester film as the dimensionally stable film, and having a 0.0005inch thick film of the thermoset epoxy polyester material laminated tothe polyester film. A film having good dimensional stability at a highertemperature such as polyester can also be laminated to a film havingless dimensional stability at the same temperature. An example of such aconstruction would be a 0.001 inch thick ethylene vinyl alcohol filmlaminated onto the 0.003 inch thick polyethylene terephthalate film.Combination films can be formed by conventional means such as adhesivelylaminating the films together with, for example, a hot melt adhesive ora laminating adhesive, coextruding the films, and extrusion coating thefilm onto the more stable film and optionally curing the coating.

The films can be heat stabilized by conventional means to improve thethermal stability of the films. Typically such a process includesheating the film without stress at a temperature above the maximum usetemperature.

The dimensionally stable film can be treated to improve adhesion of thefilm to either or both the melt sealing layer and a paint or primer.Such treatments can include corona treatment, flame treatment, chemicalpriming, chemical grafting, and the like. Treatments are especiallyuseful for polyolefin films.

In a preferred embodiment, the dimensionally stable film is attached toa second film which can provide a surface that will readily acceptstandard paints and primers, such as those used in the automotiveindustry. Examples of such films include films made from ethylene vinylalcohol and the above described epoxy polyester.

Two or more melt-flowable layers having different melt flow propertiesmay be laminated together to form a melt-flowable sheet material. Forexample, the top layer can be formulated to have greater flow propertiesthan the bottom layer, while the bottom layer is formulated to havehigher strength for better handling properties, so that on heating, thetop layer will flow and encapsulate the bottom layer.

In another embodiment, a pressure-sensitive adhesive (PSA) layer may beattached to the melt-flowable layer so that the melt-flowable sheet canbe positioned on a surface before the melt flow layer is heated. Themelt flow layer may either flow slightly to provide rounded edges on themelt-flowable sheet without flowing around the PSA, or it may flowsufficiently to encapsulate the PSA so that none of the PSA edges areexposed.

Useful PSA's include block copolymer PSA's, such asstyrene-isoprene-styrene block copolymers that can be hot melt coated orsolvent coated; acrylonitrile PSA's; acrylate PSA's, such as copolymersof acrylic or methacrylic esters of non-tertiary alcohols having fromabout 4 to 12 carbon atoms in the alcohol moiety and optionalcopolymerizable reinforcing monomers, that are polymerized using knowntechniques including solvent polymerization, emulsion polymerization,and radiation polymerization; natural rubber PSA's, silicone PSA's, andvinyl acetate PSA's. The PSA's can be bonded to the melt-flowable sheetby any known techniques including coating the PSA directly onto thesheet and curing the PSA or drying off the solvent, laminating the PSAtransfer tape to the sheet, co-extruding a hot melt PSA with themelt-flowable layer, and the like.

In a preferred embodiment, the PSA is an acrylate copolymer. Usefulesters for the copolymer include n-butyl acrylate, hexyl acrylate,2-ethylhexyl acrylate, octyl acrylate, isooctyl acrylate, decylacrylate, dodecyl acrylate, and mixtures thereof.

The copolymerizable reinforcing monomer, if used, is a monomer which hasa homopolymer glass transition temperature higher than the glasstransition temperature of a homopolymer prepared from the acrylic ormethacrylic ester. Useful reinforcing monomers include acrylic acid,isobornyl acrylate, N-vinyl pyrrolidone, acrylonitrile, N-vinylcaprolactam, N-vinyl piperidine, and N,N-dimethylacrylamide, anditaconic acid.

When a reinforcing monomer is used, the acrylic or methacrylic esterwill generally be present in an amount of about 50 to 100 parts byweight, and the reinforcing comonomer will be present in a correspondingamount of from about 50 to 0 parts by weight.

The above-described pressure-sensitive adhesives can be prepared byknown processes by mixing an initiator such as azobisisobutyronitrile inan organic solvent such as ethyl acetate, adding the monomers in thedesired proportions, and then heating at an elevated temperature such as80° C., until the polymerization is completed. The adhesives can also beprepared by UV polymerization and E-beam polymerization by processesknown in the art. Pressure-sensitive adhesives are also availablecommercially from a number of suppliers as adhesive transfer tapes. Suchtapes include product numbers 465, 467, and 468, all commerciallyavailable from Minnesota Mining and Manufacturing Co.

In an another embodiment, the melt-flowable sheet material may include alayer of a thermosettable PSA which is tacky and pressure-sensitive atroom temperature, and which cures to a thermoset adhesive after heating.This type of melt-flowable sheet material has utility in bondingtogether two surfaces with the sheet bonding to a first surface on thethermosettable PSA side at a lower temperature, i.e., about roomtemperature, and then bonding to a second surface on the melt-flowableside at a higher temperature, i.e., the melt temperature of themelt-flowable layer. When the substrates are heated at the highertemperature, the PSA also cures to form a thermoset adhesive having veryhigh bond strengths. In this application, the melt-flowable layer may beselected for minimal flow at the higher temperatures so that themelt-flowable material does not flow out of the bond.

Preferred melt-flowable layers for this embodiment include theabove-mentioned polyesters and functionalized olefinic polymers.

Suitable thermosettable PSA's include a thermosettable component and apressure-sensitive adhesive component. The thermosettable component willgenerally be present in an amount of about 25 to 150 parts by weightbased on 100 parts by weight of the PSA component.

Coatable compositions for the thermosettable PSA can be formed byvarious methods which include blending together a solvent-based PSA, athermosettable resin, and thermosettable curatives; dissolving apressure-sensitive elastomer, such as a nitrile butadiene rubber, in asolvent, and mixing with thermosettable resins and curatives; andblending monomers or prepolymers useful for making a PSA, such as themonomers for making the above-mentioned acrylate copolymers, withthermosettable resins and curatives, and photopolymerizing the blends.

Materials useful for the PSA component include those described above fora PSA. Preferred materials include acrylonitriles and acrylates, andespecially preferred are acrylates.

The thermosetting components are thermosetting resins such as epoxyresins, urethane resins, and phenolic resins. Preferred thermosettingresins are epoxies and urethanes, and epoxies are most preferred. Usefulepoxy resins are described above. The epoxy resin may be solid, liquid,or a mixture thereof, as long as the epoxy can be mixed with the PSAcomponent. Preferred epoxies include phenolic epoxy resins, bisphenolepoxy resins, hydrogenated epoxy resins, bisphenol epoxy resins,aliphatic epoxy resins, halogenated bisphenol epoxy resins, novalacepoxies, and mixtures thereof, and most preferred epoxies includediglycidyl ethers of bisphenol A.

In a preferred embodiment, the thermosettable PSA is thephotopolymerized reaction product of a composition having (i) aprepolymeric (i.e., partially polymerized to a viscous syrup typicallybetween about 100 and 10,000 centipoises) or monomeric syrup of anacrylic or methacrylic acid ester as described above; (ii) optionally, areinforcing comonomer as described above; (iii) an epoxy resin; (iv) aphotoinitiator; and (v) a heat activatable hardener for the epoxy. Theadhesives can be prepared according to the procedures found in U.S. Pat.No. 5,086,088, incorporated herein by reference.

The photoinitiators useful for polymerizing the prepolymeric ormonomeric syrup may be any conventional free radical initiatoractivatable by, for example, ultraviolet light. An example of a suitablephotoinitiator is 2,2-dimethoxy-2-phenyl acetophenone (Irgacure™651available from Ciba-Geigy Corporation). The photoinitiator is used in anamount sufficient to polymerize the monomers, typically about 0.01 to 5parts by weight per 100 parts of the prepolymeric or monomeric syrup.

The heat activatable curative is added to the composition to effectcuring of the epoxy resin when heated. The hardener may be any type, butpreferably, it is an amine type hardener such as dicyandiamide andpolyamine salts. Suitable commercial curatives are available under theOmicure™ trademark from Omicron Chemical, and under the Ajicure™trademark from Ajinomoto Chemical. The curative is used in an amountsufficient to cure the epoxy resin, typically, in an amount from 0.1 to20 parts by weight, and preferably, 0.5 to 10 parts by weight per 100parts of epoxy resin.

It is useful to further add an accelerator to the adhesive compositionbecause the heat to which the composition is exposed may be insufficientto fully activate the curing agents to cure the epoxy resin. Theaccelerator allows the adhesive to cure at a lower temperature and/orfor shorter periods of heat exposure. Imidazoles and urea derivativesare particularly preferred in the practice of the present invention anduseful compounds include 2,4-diamino-6-(2'-methylimidazole)-ethyl-s-triazine isocyanurate,2-phenyl-4-benzyl-5-hydroxymethylimidazole, hexakis (imidizole)nickelphthalate, and toluene bis-dimethylurea. The accelerator may be used inan amount up to 20 parts by weight per 100 parts by weight of the epoxyresin.

In making the melt-flowable sheet with a thermosettable PSA theaforementioned solvent based compositions are coated onto a flexibleweb, preferably a silicone coated release liner, at the desired adhesivethickness and the solvent is removed by heating the adhesive to atemperature below the thermosetting temperature. The adhesive is thenlaminated to the melt-flowable sheet for further use. Alternatively, thecompositions can be coated directly onto the melt-flowable sheet anddried at temperatures below the hot melt activation temperature.

In an alternative embodiment, a photopolymerized syrup compositionhaving the above described thermosettable PSA ingredients is prepared bycoating the syrup composition onto a silicone release liner andphotopolymerizing in an inert atmosphere, i.e., substantiallyoxygen-free atmosphere, e.g., a nitrogen atmosphere, and irradiating thecomposition with ultraviolet light. A sufficiently inert atmosphere canbe achieved by covering the coating with a second polymeric film whichis substantially transparent to UV radiation, and irradiating throughthe film. The adhesive is then laminated to the melt-flowable layer.Alternatively, a sheet of melt-flowable layer may be used in place ofeither the top or the bottom release liner.

Further, a nonwoven or reinforcing scrim may be inserted between thelayers or embedded within the thermoset PSA layer to provide additionalstrength for handling purposes.

The aforementioned melt-flowable sheet having a thermosettable PSA isparticularly useful for washer bonding in assembling automobiles. Thewasher is prepared by laminating the washer to a piece of thethermosettable PSA that has been cut, e.g., die cut or punch pressed, tothe size and shape of the washer. The cut thermosettable PSA is thenlaminated to the washer by hand or by robotized machinery with themelt-flowable side exposed and available for bonding at highertemperatures. Alternatively, the thermosettable PSA is bonded to a sheetof metal suitable for making washers. The melt-flowable layer of thesheet is tack-free at room temperature. Washers of the desired dimensionare then stamped from the metal sheet.

In use, the washer is used to tighten a bolt to a door hinge as the dooris aligned and attached to the automobile frame. The automobile is thenpainted and put through oven curing cycles to dry and cure the paint.The melt-flowable side of the sheet also melts sufficiently in the ovento bond aggressively to the metal surface of the frame. The doors arethen removed for installing interior parts, and the doors can bere-attached in the aligned position as indicated by the position of thewashers. This method of washer bonding allows for automatic dispensingof the washers in assembly as well as eliminating liners and adhesivecontamination problems associated with previously known methods ofbonding washers.

In the washer bonding application the melt-flowable sheet is preferablyfrom about 10 to 250 micrometers thick, and most preferably, 25 to 100micrometers thick. Thicknesses greater than about 250 micrometers mayresult in leaking of the melt-flowable material from the washer duringthe thermosetting operation which can affect the strength of the bondbetween the washer and the automobile frame. The thermosettingpressure-sensitive adhesive layer should range from about 10 to 300micrometers, and preferably, from about 30 to 200 micrometers.

TEST PROCEDURES

OVERLAP SHEAR STRENGTH

Two 2.5 cm by 5 cm PPG ED-11 panels (electrodeposition primed steelavailable from Advance Coating Technologies, Inc., also referred toherein as ED-11 panels) were bonded with a 2.54 cm×1.27 cm overlap areausing a strip of melt-flowable tape measuring 2.54 cm by 1.27 cm. Thesample is heated to bond the two panels together at temperaturesindicated in the specific examples and then cooled to room temperaturefor at least 16 hours. The panels are then tested in an Instron™ tensiletesting machine using a crosshead speed of 5 cm per minute. The force atadhesive failure is recorded in megaPascals (MPa).

ADHESIVE SHEAR STRENGTH FOR WASHER BONDING

The adhesive shear strength was measured according to JISK6850. Two 1.6mm thick steel panels were used as the substrates. The adhesive isplaced between the panels and then cured at a temperature of 140° C.with a pressure of 500 g/cm² for 60 minutes. The panels are then cooledto room temperature before testing. Using a tensile tester, the adhesiveshear strength is measured at a jaw separation rate of 50 mm/min.

The preferred adhesives have a shear strength greater than 50 kgf/cm².

PUNCHING ABILITY

A pressure operated punch press was used to punch the bonding materialsin the form of a circle corresponding to the hole in a washer with apressure of 30 kgf/cm². The number of samples per bonding material wasfive. The samples were assessed under the criteria below.

Good: no punching failure. The pressure-sensitive thermosetting adhesivedoes not leak out of the hot melt film. The cross section looks good.

Relatively hard to punch: one or two samples are punched imperfectly.The thermosetting adhesive slightly leaks out of the hot melt film.

LEAKAGE OF AN ADHESIVE AGENT

The samples used in measuring the adhesive shear strength were used tovisually check for leakage of a pressure-sensitive thermosettingadhesive or the hot melt film from the steel panels. The criterion ispresented below:

No leakage: Ok

Slight amount of leakage: Fair

Large amount of leakage: Poor

Specific embodiments of the invention will be illustrated by thefollowing nonlimiting examples. Parts refer to parts by weight unlessotherwise indicated.

EXAMPLES 1-2

For Example 1 (EX-1), a melt-flowable sheet was prepared by heating 100parts of a hydroxy-functional semi-crystalline polyester resin(Dynapol™1402 available from Huls America) to about 110° C. to form amolten mixture. The molten mixture was coated on a knife bar coater(heated to 127° C.) onto a silicone coated kraft paper to form a 1.0 mmthick sheet. The sheet was cooled to room temperature and became opaqueafter about 2 hours indicating that crystallization had occurred.

For Example 2 (EX-2), a melt-flowable sheet was prepared by mixing 10parts of a digylcidyl ether of bisphenol A (EPON™828, available fromShell Chemical Company) with 89 parts DYNAPOL™S1402 and 1 part triphenylsulfonium hexafluoroantimonate (described in U.S. Pat. No. 4,321,951,column 5, line 48, to column 7, line 48), and mixing at about 110° C.for about an hour. The resulting mixture was coated on a knife barcoater (heated to 127° C.) onto a silicone coated kraft paper to form a1.0 mm thick sheet. The sheet was cooled to room temperature.

TESTING OF EXAMPLES 1 & 2

Sample tapes of Examples 1 and 2 measuring about 2.5 cm by 7.6 cm wereplaced across a 2.5 cm wide strip of anodized aluminum positioned acrossa larger anodized aluminum panel (referred to hereinafter as a steppanel), and heated in an oven at 177° C. for 30 minutes. Both tapesflowed out and provided aesthetically pleasing smooth surfaces withrounded corners and smooth transitions between the aluminum strip andthe panel. The tapes also flowed out beyond the original dimensions ofthe strips on the panels and adhered tenaciously to the panels.

Each example was then cut into strips 1.9 cm wide and about 25.4 longand placed into U-channels having an inside width of 1.9 cm. EachU-channel was formed by bending two pieces of cold rolled steel at 90°angles and spot welding the pieces together so that a step down jointwas formed in the U. The U-channels, with the strips attached, weretilted at an angle of about 15° and heated in an oven at 177° C. for 30minutes and cooled to room temperature. Both strips had flowed out toeffectively seal the joint and impart a smooth surface in the channelwith no appearance of the step joint on the surface.

The lower edge of both strips were marked on the U-channel and bothU-channels were then placed in a 120° C. oven at a 15° angle for 30minutes, and then cooled. The flow from subsequent heating was about 3.2mm on EX-1 and about 25.4 mm on EX-2.

An additional sample of each of EX-1 and EX-2 was tested on step panelsas described above and heated for 30 minutes at 177° C. All four samples(the two original samples exposed to previous heating cycles and the twonew samples with no exposure to subsequent heating cycles) were paintedwith a white water-borne base coat (HWB90934 available from PPGIndustries) and heated for 5 minutes at 121° C. A two part clear coat(CNCT2AH Part A and CNCT2BE Part B, both available from PPG Industries)was mixed according to the manufacturer's instructions and spray paintedon all four panels. The panels were then heated for 30 minutes at 140°C. and cooled. The paint finish on the melt-flowable strips wasidentical in gloss, color, and distinctness of image (which is anindication of its mirror-like qualities) as the surrounding metalsurface. The paint transition between the melt-flowable strip and themetal surface was smooth and exhibited no evidence of a parting line orpaint edge separation.

The samples that had been heated once to melt flow the tapes prior topainting were then placed in an oven at 120° C. for 30 minutes. Aftercooling, no additional flow was observed in either panel and the surfaceremained smooth and aesthetically pleasing. The panel with themelt-flowable strip of EX-2 exhibited slight wrinkling at the surface atoven temperatures, but the wrinkles disappeared on cooling to roomtemperature.

The foregoing Examples and tests illustrate preferred embodiments of theinvention wherein sealed, aesthetically pleasing, and paintable surfacesare imparted to a metal surface.

EXAMPLE 3

The melt-flowable layer of EX-1 was cut into a strip measuring 2.5 cm by7.6 cm, placed on an ED-11 panel, and heated in a 177° C. oven for 30minutes. The panel was then cooled, painted with the white base coat andclear coat paints described above, and placed in a 121° C. oven for 30minutes to cure the paint. The melt-flowable tape produced aprotuberance having rounded edges on the panel. Subsequent heating ofthe panel placed horizontally in a 177° C. oven for 30 minutes did notaffect the paint surface or any distortion to the protuberance. Thepanel was then placed in a 177° C. oven for 30 minutes at a 75° anglefrom the horizontal. As the panel heated, a protuberance formed into ateardrop shape with the paint surface remaining intact. The panel wascooled to room temperature in the 75° angle position and theprotuberance returned to its original shape.

The same panel was reheated at a 75° angle except that a pinhole waspunched through the paint layer into the melt-flowable layer. Uponheating, the underlying melt-flowable layer was still thermoplastic andoozed out of the pinhole.

The foregoing example illustrates the formation of a reacted interfacebetween the paint and the melt-flowable sheet material.

EXAMPLE 4

A strip of the melt-flowable sheet of EX-1 measuring about 2.5 cm by 7.6cm was placed on a silicone release coated polyester film and placed inan oven at 177° C. until the tape became clear, indicating that it hadbecome amorphous. The strip was removed from the oven and cooled to roomtemperature (between 21° C. and 23° C.). The strip, still clear, hadsufficient tack to adhere to an ED-11 at room temperature. The panel wasthen heated to adhere the strip to the panel at 120° C. for 10 minutes,and then reheated at 177° C. for 30 minutes. The sample was thenpainted, and cured in a 140° C. oven for 30 minutes. This exampleillustrates how an embodiment of the invention can be temporarilypositioned on a substrate before permanently bonding to the substrate.

EXAMPLE 5

The melt-flowable sheet material of EX-1 was laminated to an acrylatePSA transfer tape (467 Adhesive Transfer Tape, available from MinnesotaMining & Manufacturing Co.). Strips measuring 2.5 cm by 7.6 cm werelaminated to an anodized aluminum panel, and 2.54 cm by 1.27 cm stripswere laminated to the ED-11 overlap shear panels described above. Thesamples were placed in an oven for 15 minutes at 177° C. and then cooledat room temperature until they were opaque (about 90 minutes).

The sample on the anodized aluminum panel adhered well and themelt-flowable sheet had encapsulated the PSA. The lap shear samples weretested and had an average overlap shear strength of 253.8 pounds persquare inch. The failures were observed to be cohesive between the PSAand the melt-flowable sheet.

The above example illustrates the utility of a PSA layer on themelt-flowable sheet to hold the sheet in place until it is heated toseal a surface.

EXAMPLES 6-10

Two hydroxy-functional polyesters having different amounts ofcrystallinity were mixed and coated to form sheets as described inEX- 1. The time required for the sheets to turn opaque was measured asan indication of the rate of crystallization. The polyester materialsused were Dynapol™1402, a weakly crystalline polyester resin andDynapol™1359, a polyester resin with higher crystallinity. The amountsof each resin are shown in Table 1. The details shown in Table 1indicate that the rate of crystallization can be varied.

                  TABLE 1                                                         ______________________________________                                                  EX-6  EX-7    EX-8    EX-9  EX-10                                   ______________________________________                                        Dynapol ™S1402                                                                         100     75      50    25    0                                     Dynapol ™S1359                                                                         0       25      50    75    100                                   Crystallization Time                                                                      140     110     15    9     7                                     (min.)                                                                        ______________________________________                                    

EXAMPLES 11-18 AND C1-C3

Various thermoplastic materials were evaluated for flow and paintadhesion. The materials were provided in 1 mm to 3 mm thick sheets.Example 11 was prepared as in EX-1 except that a 1 mm thick sheet wasprepared, and Example 12 was prepared as in EX-2 except with a thicknessof 1 mm. The remaining sheets were prepared by placing pellets of thematerials between release coated polyester liners and heating with aniron until the materials fused into sheets between about 0.08 mm and0.15 mm in thickness. Multiple sheets were folded together to formthicker sheets measuring between about 1 and 3 mm.

The samples were placed on step panels (described above) at 177° C. for20 minutes and the flow properties were noted.

The samples were then painted with a white water-borne base coat(HWB90934 available from PPG Industries) and heated for 5 minutes at140° C. A two part clear coat (CNCT2AH Part A and CNCT2BE Part B, bothavailable from PPG Industries) was mixed according to the manufacturer'sinstructions and spray painted on the panels. The panels were thenheated for 30 minutes at 140° C. and cooled overnight. The panels werethen reheated to 140° C. for 20 minutes.

The materials were tested as follows: (1) for flow after heating, butbefore painting (OK indicates that the material flowed but remainedviscous; L indicates that the material liquified); (2) paint qualityafter painting, curing the paint, and re-heating (OK indicates surfaceappearance was good; FAIL indicates that the paint cracked or did notcure); (3) after reheating (OK indicates no change in appearance; EDGEindicates that the paint cracked around the perimeter of the sheet andFAIL indicates that the paint cracked and polymer flowed out of thecracks); and (4) for cross hatch adhesion reported as a percentage ofthe paint still adhered to the melt-flowable sheet, testing per ASTMD3359-90 to get (100% is desired, FAIL indicates sample failed beforetest could be performed). Test results are detailed in Table 2.

                  TABLE 2                                                         ______________________________________                                             Melt-    Heated 20                                                                              Painted & Reheated                                                                             Paint                                      flowable min. at  Heated 30 20 min. at                                                                           Adhesion                              EX.  Material 350° C.                                                                         min. @ 141° C.                                                                   141° C.                                                                       %                                     ______________________________________                                        11   EX-1     OK       OK        OK     100                                   12   EX-2     OK       OK         OK*   100                                   13   A        OK       OK        OK      100**                                14   B        OK       OK        EDGE   100                                   15   C        OK       OK        OK     100                                   16   D        OK       OK        FAIL    100**                                17   E        OK       OK        FAIL    20                                   18   F        OK       FAIL      FAIL   FAIL                                  C1   G        L        FAIL      FAIL   FAIL                                  C2   H        L        FAIL      FAIL   FAIL                                  C3   I        L        FAIL      FAIL   FAIL                                  ______________________________________                                         A -- TS1502 available from Sherex Co.                                         B -- BUTVAR ™B79 -- polyvinylbutyral from Monsanto Co.                     C -- Surlyn ™1605 -- ethylene acrylic acid film from DuPont Co.            D -- Primacor ™3440 -- ethylene acrylic acid from Dow Chemical Co.         E -- Elvax ™260 -- ethylene vinyl acetate from DuPont Co.                  F -- SCX 8008 -- acrylic polyol from J. C. Johnson Co.                        G -- Carbowax ™8000 from Union Carbide                                     H -- Carbowax ™20M from Union Carbide                                      I -- TMP (trimethylolpropane) from Aldrich Chemical                           *Paint sufface wrinkled when hot; surface smoothed out on cooling             **Paint film was brittle                                                 

EXAMPLES 19-21

Example 19 is a melt-flowable sheet made as in EX-1 except to athickness of about 2 mm. Example 20 was prepared using two sheetsprepared as in EX-1 to a thickness of 1.27 mm with a nylon nonwovenbetween the two sheets. The nonwoven was a 0.3 ounce/square yard(CEREXT™ available from Fiberweb N.A.) and was laminated to the firstsheet between two silicone coated polyester release liners with a heatediron. The second sheet was then laminated in a similar manner. Thesheets had turned transparent during the lamination process. Example 21was prepared as Example 20 except that a polyester nonwoven material(0.5 oz/sq. yd. Reemay 2250, available from Reemay) was used.

Examples 19-21 were tested by cutting 2.54 cm by 20.3 cm strips andplaced lengthwise on a curved metal surface that was formed by bending aED-11 primed metal panel such that it swept at an angle starting atabout 30° from the horizontal. The bent panel was placed in an oven at177° C. for 10 minutes. After cooling, Example 19 was observed to havesignificant flow down the sides of the panel. Example 20 had a slightamount of flow but had shrunk about 8% due to shrinkage of the nylon.Example 21 also had a slight amount of flow but no shrinkage.

The foregoing examples illustrate how a nonwoven scrim can be used tocontrol the flow of the melt-flowable sheet.

EXAMPLES 22 And 23

Sheets were prepared as in EX-2 to a thickness of 0.076 mm. The sheetfor Example 22 was exposed to UV radiation (low intensity black light)for 5 minutes. The sheets for each example were then cut and layered tomake 0.72 mm thick sheets. The sheets were then cut into 2.54 cm by 7.62cm strips, draped over two overlapping metal panels, and then heated at177° C. for 30 minutes. FIGS. 5a and 5b depict the panels and a sheetbefore (FIG. 5a) and after heating (FIG. 5b). The panels were cooled andboth examples exhibited sufficient flow to seal the seam. Example 23,the sample that was not irradiated had a smoother profile over the stepin the overlapping panels and the step in panels was more pronounced inExample 22. The panels were then coated with a black base coat fromBASF, cured, overcoated with a two part clear coat, and cured. Bothsamples painted well and cross hatch adhesion was 100%.

The above examples illustrate how irradiating the sheet material canchange the surface conformability.

EXAMPLE 24

A crosslinkable melt-flowable sheet was prepared as in EX-2 except thatthe composition was prepared by mixing 10 parts of a cycloaliphaticepoxy (ERL-4221 available from Union Carbide) with 89 parts of a weaklycrystalline saturated linear copolyester (DYNAPOL™S1402) and 1 parttriphenyl sulfonium hexafluoroantimonate, and coating to a thickness of2 mm. A second melt-flowable sheet was prepared as in EX-1 except thethickness was 2 mm. The two sheets were placed on top of each other andbetween silicone release coated polyester liners, and heated at 177° C.for 10 minutes to form a 4 mm thick sheet. A strip was cut to a width ofabout 2.54 cm and placed into a roof ditch prototype having a width of1.25 cm and a depth of about 1.9 cm, with the cross-linkable sheet ontop. The prototype with the strip was placed in an oven at 177° C. for20 minutes. After cooling, the strip had maintained an aestheticallypleasing concave surface along the length of the prototype. The bottomlayer had melted and flowed into the joint in the prototype and thesides of the tape had bonded tenaciously to the sides of the ditch toeffectively seal the ditch. Some entrapped air bubbles were seen andthese may have been related to the thickness of the tape.

EXAMPLE 25

The 2 mm thick crosslinkable melt-flowable sheet of Example 24 wasexposed to UV black light for 20 seconds to photolyze the surface with atotal energy of 160 mJ/cm² (millijoules per square centimeter) using aUvirad radiometer (Model No. VR365CH3) from E.I.T. (ElectronicsInstrumentation & Technology, Inc., Sterling, Va.). A strip was cut asin example 24, creased lengthwise with the photolyzed side in, and thenplaced into a prototype roof ditch as described in Example 24, with thephotolyzed side up. The prototype was then heated at 177° C. for 20minutes. The thinner strip provided a smoother transition line betweenthe strip and the sides of the roof ditch prototype, while providing atenacious bond to the sides of the prototype. Some entrapped air wasobserved between the strip and the prototype, but bubbles did not affectthe aesthetically pleasing surface characteristics of the strip.

EXAMPLES 26-34

Melt-flowable sheets were prepared as described in EX-2 except that thecompositions and materials were changed as shown in Table 3. Examples26-31 were 2 mm thick and Examples 32-34 were 1 mm thick. All of theexamples exhibited good flow properties and paint adhesion was 100% forall of the samples.

                  TABLE 3                                                         ______________________________________                                        Melt-flowable Compositions                                                             Epoxy           Catalyst                                             EX      PET    1         2   3       1   2                                    ______________________________________                                        26      94     5                     1                                        27      96     3                     1                                        28      89     10                    1                                        29      94               5           1                                        30      96               3           1                                        31      89               10          1                                        32      89                   10          1                                    33      94                   5           1                                    34      96                   3           1                                    ______________________________________                                         PET -- Dynapol ™S1402                                                      Epoxy I -- diglycidyl ether oligomer of bisphenolA (Epon ™1001,            available from Shell Chemical Co.)                                            Epoxy 2 -- Epon ™1002                                                      Epoxy 3 -- diglycidyl ether of bisphenolA(Epon ™828, available from        Shell Chemical Co.)                                                           Catalyst 1 -- triphenyl sulfonium hexafluoroantimonate                        Catalyst 2 -- described in U.S. Pat. No. 5,089,536                            (eta.sup.6xylenes (mixed isomers))(eta.sup.5 cyclopentadienyl) iron (1+)      hexafluoroanimonate.                                                     

EXAMPLE 35

A 0.254 mm thick melt-flowable sheet was prepared as in Example 1. Thesecond layer was prepared as follows:

A 50/50 mixture of butyl acrylate and N-vinyl caprolactam was mixed toform a solution. A melt-flowable composition (57.7% acrylate and 42.3%epoxy) was prepared by mixing 75 parts of butyl acrylate, 75 parts ofthe butylacrylate/N-vinyl caprolactam solution, 50 parts of a butylmethacrylate/methyl methacrylate copolymer (Acryloid™B-60, availablefrom Rohm and Haas, Co.) and 110 parts of a diglycidyl ether oligomer ofbisphenol-A (Epon™1001) in a jar on a roller mill until the epoxy andcopolymer were in solution. To the solution were added 0.15 part of2,2-dimethoxy-2-phenyl acetophenone (Irgacure™651, available fromCiba-Geigy), 0.15 part anti-oxidant (Irganox™1010, available fromCiba-Geigy), 1.0 part carbon tetrabromide, 3.86 parts dicyandiamide(DYHARD™100, available from SKW Chemical), 1.38 parts hexakis(imidizole)nickel phthalate, 2 parts glass bubbles (C 15-250 GlassBubbles available from Minnesota Mining and Manufacturing Co.), and 7parts of silica (Cab-o-sil™M-5, available from Cabot Corp.). Thecomposition was mixed with a high shear mixer and then mixed on a rollermill for about 24 hours. The composition was then degassed and knifecoated to a thickness of about 2.0 mm between 0.05 mm thick polyesterliners which had been silicone coated. The coated composition was thenexposed to ultraviolet light sources having 90% of the emissions between300 and 400 nm with a maximum at 351 nm. The light intensity above theweb was 1.88 mW/cm² (milliwatts/square centimeter) and 1.29 mW/cm². Thetotal energy used was 653.8 millijoules. The resulting melt-flowabletape was substantially tack-free at room temperature (about 21° C.).

One of the polyester liners was removed from each of the sheets, and thefirst and second melt-flowable sheets were laminated together with aniron set at about 65.6° C. to form a melt-flowable composite sheet.

A strip of the composite sheet was placed on a metal panel having aslight depression on the surface with the first layer of the sheet onthe metal surface, heated to 177° C. for 30 minutes, and then cooled toroom temperature. Example 38 showed no surface defects from thedepression. As a comparison, a sheet having only the second layerdescribed above was tested in the same manner. The surface of the secondsheet had a visible crater in the sheet overlaying the depression.

EXAMPLE 36

A melt-flowable sheet was prepared by extruding a 0.076 mm thick layerof an ethylene acrylic acid having a 9% acrylic acid content (PRIMACOR3440, available from Dow Chemical Co.) on a flat T die set at about 250°C.

A 50/50 mixture of butyl acrylate and N-vinyl caprolactam was heated toabout 50° C. to form a solution. A melt-flowable composition (50%acrylate and 50% epoxy) was prepared by mixing 120 parts of butylacrylate, 80 parts of the butylacrylate/N-vinyl caprolactam solution, 50parts of a butyl methacrylate/methyl methacrylate copolymer(Acryloid™B-60, available from Rohm and Haas, Co.) and 200 parts of adiglycidyl ether oligomer of bisphenol-A (Epon™1001, available fromShell Chemical Co.) in ajar on a roller mill until the epoxy andcopolymer were in solution. To the solution was added 0.2 part of2,2-dimethoxy-2-phenyl acetophenone (KB-1, available from Sartomer), 0.2part anti-oxidant (Irganox™1010, available from Ciba-Geigy), 0.8 partcarbon tetrabromide, 7.0 parts dicyandiamide (DYHARD™100, available fromSKW Chemical), 3.0 parts hexakis (imidizole)nickel phthalate, 4 partsglass bubbles (C15-250 Glass Bubbles, available from Minnesota Miningand Manufacturing Co.) and 14 parts of silica (Cab-o-sil™M-5 availablefrom Cabot Corp.) to form a mixture. The mixture was mixed, coated, andcured according to the procedure of Example 38 to form a melt-flowabletape.

An adhesive composite was prepared by laminating the hot melt adhesivelayer to the thermosettable melt-flowable tape with an iron as describedabove.

EXAMPLE 37

A pressure-sensitive adhesive composition was prepared by mixing 76parts of butyl acrylate, 24 parts N-vinyl pyrrolidone, and 0.04 partsIrgacure™651 photoinitiator (2,2-dimethoxy-2-phenyl acetophenoneavailable from Ciba Geigy) and photopolymerizing with an ultraviolet(UV) light source under a constant nitrogen purge to form a syrup havinga viscosity of about 2000 cps. With constant mixing, the followingmaterials were added to 100 parts of the acrylate syrup and mixed forabout two hours: 0.1 parts Irgacure™651, 40 parts diglycidyl etheroligomer of bisphenol-A (Epikote™1001 available from Shell ChemicalCo.), 50 parts diglycidyl ether of bisphenol A (ELA 128 available fromShell Chemical Co.), 6.0 parts dicyandiamide (CG1200 from OmicronChemical Co.), 3.5 parts2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-S-triazine isocyanurateadduct (2MA-OK available from Shikoku Chemical Co., Ltd.), 5.0 partsfumed silica (Aerosil™972 available from DeGussa), and 0.03 parts ofhexanediol diacrylate. The mixture was then degassed, and knife coatedto a thickness of 0.3 ounces per square yard on top a polyamide nonwoven(CEREX from Fiberweb N.A.) placed on top of a transparent siliconecoated polyester release liner having a thickness of about 0.05 mm. Asimilar release liner was placed on top of the coated composite, and thecoated mixture was photopolymerized with ultraviolet lamps at an averageintensity of about 1.1 mW/cm² above and below the web, such that a totalenergy of 500 mJ/cm² were used. The lamps used had about 90% of theemission between 300 and 400 nm, with a maximum at 351 nm. The resultingthermosetting pressure-sensitive adhesive tape (TPSA) layer had athickness of about 0.3 mm.

A hot melt adhesive layer (HMA) was prepared by extruding an ethyleneacrylic acid polymer having an acrylic acid content of 6.5%(PRIMACOR™3330, available from Dow Chemical, Ltd.) at a temperature ofabout 250° C. using a T die. The thickness of the layer was 50micrometers.

An adhesive tape composite was prepared by removing one of the linersfrom the pressure-sensitive adhesive tape and laminating the hot meltadhesive layer to it. The composite was tested for adhesive shearstrength, punching ability, and leakage. Test results are shown in Table4.

EXAMPLE 38

A thermosetting pressure-sensitive adhesive was prepared by dissolving150 grams of an acrylonitrile rubber (Nippol 1001 available from NipponZeon Co., Ltd.) in 400 grams of methyl ethyl ketone. The followingmaterials were then added to the solution and mixed for 24 hours toobtain a homogeneous mixture: 100 grams of Epikote™828, 100 gramsEpikote™1001, 20 grams dicyandiamide, 235 grams Amicure PN (epoxycurative available from Ajinomoto Co., Inc.), and 20 grams of silicapowder (Aerosil™A-200 available from Nippon Aerosil Co., Ltd.). Themixture was then knife coated on a silicone coated polyester liner, anddried for 15 minutes at 70° C. The resulting thermosettablepressure-sensitive adhesive layer had a thickness of 100 micrometers.

An adhesive composite was prepared by laminating the thermosettablepressure-sensitive adhesive layer to a 50 micrometer hot melt adhesivelayer prepared as described in Example 37. Test results are shown inTable 4.

EXAMPLES 39-42

Adhesive composites were prepared as described in Example 38 havingvarying thicknesses of each layer as shown in Table 4. Test results arealso shown.

                  TABLE 4                                                         ______________________________________                                             TPSA      HMA       Shear         Leakage of                                  Thickness Thickness Strength                                                                             Punching                                                                             Bonding                                EX   Micrometers                                                                             Micrometers                                                                             kg/cm.sup.2                                                                          ability                                                                              Material                               ______________________________________                                        37   300       50        Not tested                                                                           OK     OK                                     38   100       50        162    OK     OK                                     39   100       100       175    OK     OK                                     40   100       200       166    OK     OK                                     41    50       100       164    OK     OK                                     42   360       50        Not tested                                                                           Not tested                                                                           Not tested                             ______________________________________                                    

EXAMPLES 43-46

The thermosetting pressure-sensitive adhesives of Example 37 werelaminated onto various hot melt adhesive layers as shown in Table 5. Thethermosetting pressure-sensitive adhesive layer was 100 micrometersthick. The hot melt adhesive layers were prepared by extruding the hotmelt adhesive resins shown in Table 5. Test results are shown in Table6.

                  TABLE 5                                                         ______________________________________                                            Resin    Product         Melting Thickness -                              EX  Type     Designation/Manufacturer                                                                      Point - (° C.)                                                                 micrometers                              ______________________________________                                        43  Olefinic DAF-899/Dow Chemical,                                                                         83      75                                                    Ltd.                                                             44  Olefinic 8930/Toray Synthetic Film                                                                     90      50                                                    Corp.                                                            45  Polyester                                                                              4152B/Toray Synthetic                                                                         120     65                                                    Film Corp.                                                       46  Polyester                                                                              1152B/Toray Synthetic                                                                         80      65                                                    Film Corp.                                                       ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                                              Punching Leakage of                                     EX   Shear Strength - kg/cm2                                                                        Ability  Bonding Material                               ______________________________________                                        43   170              OK       OK                                             44   90               OK       OK                                             45   165              OK       OK                                             46   174              OK       OK                                             ______________________________________                                    

EXAMPLE 47

A first radiation curable epoxy polyester composition was prepared byblending 88.9 parts by weight of a hydroxy-functional semi-crystallinepolyester resin (Dynapol™S1359 available from Huls America) and 1 partmicrocrystalline wax (Unilin™700 available from Petrolite Corp.). Aliquid mixture having 10 parts epoxy resin (Epon™828), and 1 parttriphenyl sulfonium hexafluoroantimonate was pumped into the extruder atabout the midpoint of the barrel and mixed with the polyester resinmixture. A vacuum of less than 25 inches Hg was applied in the extruderbarrel at the same area in the extruder barrel to eliminate air from themixture. The extruder barrel temperatures ranged from 65C to 110C withthe feed port temperature at about 25C. The flat die was maintained at atemperature of 82C. The extrudate was coated onto an untreated 0.00291inch thick polyester film, and the coated film was wound into a rollafter cooling. The extrudate thickness ranged from 0.0005 to 0.0007inch.

The coating on the polyester film was then exposed to an ultravioletlight (UV) processor (Model QC250244ANIR supplied by AetekInternational, Plainfield Ill.) with one medium pressure UV lamp havingan energy output of 0.201 J/cm² at a line speed of 30 feet per minute.The resulting coating on the polyester film was thermoset and hadexcellent adhesion to the polyester film.

The other surface of the polyester film was then coated with a secondepoxy polyester composition prepared in the same manner as the firstepoxy polyester composition, except that the dry composition was 77.9parts Dynapol™S1359, 1 part microcrystalline wax (Unilin™700) and theliquid mixture contained 20 parts epoxy resin (Epon™828), 1 part polyol(Voranol™230-238 Polyol available from Dow Chemical Co.), and 0.1 partCp(xylenes)Fe⁺ SbF₆ ⁻. The second epoxy polyester composition was coatedto a thickness of 0.040 inch on the polyester film to form a sheetmaterial.

EXAMPLE 48

The second epoxy polyester composition of Example 47 was coated to athickness of 0.040 inch onto a 0.007 inch thick filled ultrahighmolecular weight polyolefin film (Teslin™sp 700 available from PPGIndustries, Inc.) to form a sheet material.

A 2.5 inch wide by 10 inch long strip of the sheet material was appliedto an anodized aluminum panel and heated at 177C for 15 minutes. Aftercooling the crossweb shrinking was determined to be 0% and the downwebshrinkable was about 1.5%.

EXAMPLE 49

A film layer was prepared by laminating a 0.00265 inch thick polyesterfilm (Melinex 054 primed polyester film, 2.65 mils, from ICI Films, WestChester, Pa.) to a 0.025 mm thick ethylene vinyl alcohol film having 44mole percent ethylene (E-25 from EVAL) with a polyester/isocyanatelaminating adhesive (Adcote 76T3A/Catalyst F, available from Morton)diluted to a solids content of 30% using ethyl acetate. The adhesive wasapplied to the ethylene vinyl alcohol film at a dry coating weight ofabout 32 grams per square meter using a gravure coater. The adhesive wasdried at about 63C to evaporate the solvent. The polyester film was thencorona treated and heat laminated to the adhesive coated side of theethylene vinyl alcohol film using nip rollers at about 93C.

The polyester side of the film laminate was then coated with a 0.040inch thick layer of the second epoxy polyester composition as describedin Example 47.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the method and article ofthe present invention without departing from the spirit or scope of theinvention. Thus, it is intended that the present invention cover themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

We claim:
 1. A article adapted for placement on the surface of asubstrate comprising:(a) a melt-flowable composition that flows andsubstantially covers a desired area of the surface of the substrate whensaid article is heated to a temperature sufficient to cause saidmelt-flowable composition to flow; and (b) a dimensionally stable filmfor controlling the melt-flow behavior of said melt-flowable compositionto substantially confine said melt-flowable composition to the desiredarea of the surface of the substrate when said article is heated to atemperature sufficient to cause said melt-flowable composition to flow,said dimensionally stable film having a preselected surface topographywhich is substantially retained when said article is heated to atemperature sufficient to cause said melt-flowable composition to flow,said dimensionally stable film having sufficient integrity such that:(i)it does not melt and flow when heated to temperatures sufficient tocause said melt-flowable composition to melt and flow.
 2. An articleaccording to claim 1 wherein said melt-flowable composition comprises athermoplastic composition.
 3. An article according to claim 1 whereinsaid melt-flowable composition comprises a thermosetting composition. 4.An article according to claim 1 wherein said melt-flowable compositioncomprises a semi-crystalline, thermosetting composition comprising anepoxy-polyester blend.
 5. An article according to claim 1 wherein saidmelt-flowable composition comprises a thermosetting compositioncomprising an epoxy-acrylate blend.
 6. An article according to claim 1wherein said melt-flowable composition comprises a first melt-flowablelayer and a second melt-flowable layer in which said first melt-flowablelayer flows to a greater extent than said second melt-flowable layerwhen said article is heated to a temperature sufficient to cause saidmelt-flowable composition to flow, said first melt-flowable layer beingadapted for placement on the surface of the substrate.
 7. An articleaccording to claim 1 wherein said melt-flowable composition comprises afirst melt-flowable layer and a second melt-flowable layer adapted forplacement on the surface of the substrate in which said secondmelt-flowable layer flows to a greater extent than said firstmelt-flowable layer when said article is heated to a temperaturesufficient to cause said melt-flowable composition to flow tosubstantially encapsulate said first melt-flowable layer.
 8. An articleaccording to claim 1 wherein said melt-flowable composition comprises athermally activated expansion agent.
 9. An article according to claim 1wherein said melt-flowable composition comprises a photo-curable,melt-flowable layer and a thermally curable, melt-flowable layer.
 10. Anarticle according to claim 1 wherein said article is adapted forplacement on the surface of a metal joint of a vehicle.
 11. An articleaccording to claim 1 wherein said article is adapted for placement onthe surface of a roof ditch of a vehicle.
 12. An article according toclaim 1 wherein said dimensionally stable film comprises an ultra-highmolecular weight polyolefin.
 13. An article according to claim 1 whereinsaid dimensionally stable film comprises an ultra-high molecular weightmicroporous polyolefin.
 14. An article according to claim 1 wherein saiddimensionally stable film comprises an oriented polyester.
 15. Anarticle according to claim 1 wherein said dimensionally stable filmcomprises oriented polyethylene terephthalate.
 16. An article accordingto claim 1 wherein said dimensionally stable film comprises a B-stagedthermosetting composition.
 17. An article according to claim 16 whereinsaid B-staged thermosetting composition comprises a B-stagedepoxy-polyester blend.
 18. An article according to claim 1 wherein saiddimensionally stable film comprises a substantially smooth surfacetopography.
 19. An article according to claim 1 wherein saiddimensionally stable film comprises a substantially smooth,paint-receptive surface that remains substantially smooth after saidarticle has been placed on the surface of a substrate, heated to atemperature sufficient to cause said melt-flowable composition to flow,and then cooled.
 20. An article according to claim 19 wherein saiddimensionally stable film comprises a substantially smooth,paint-receptive surface comprising a thermosetting epoxy-polyesterblend.
 21. An article according to claim 19 wherein said dimensionallystable film comprises an oriented polyester film provided on one surfacewith a thermosetting epoxy-polyester blend.
 22. An article according toclaim 19 wherein said dimensionally stable film comprises asubstantially smooth, paint-receptive surface comprising anethylene-vinyl alcohol film.
 23. An article according to claim 1 whereinsaid dimensionally stable film exhibits a downweb and crossweb shrinkageof less than about 5% when heated at a temperature sufficient to causesaid melt-flowable composition to flow.
 24. An article according toclaim 1 wherein said dimensionally stable film exhibits a downweb andcrossweb shrinkage of less than about 2% when heated to a temperaturesufficient to cause said melt-flowable composition to flow.
 25. Anarticle according to claim 1 wherein said dimensionally stable filmexhibits a downweb shrinkage of less than about 1% and a crosswebshrinkage of less than about 0.5% when heated to a temperaturesufficient to cause said melt-flowable composition to flow.
 26. Anarticle according to claim 1 wherein said melt-flowable compositioncomprises a plurality of melt-flowable layers in which the melt-flowableproperties of the individual layers are tailored such that said layerscooperate with each other to achieve the desired coverage of saidsurfaces.